1. Field of the Invention
The present invention relates to a contaminant removal system, and more particularly, to an apparatus for cleaning contaminants from the surface of a dryer roll, in a paper making machine, adjacent a doctor blade.
2. Description of the Prior Art
Doctor blades are utilized, in paper making, to clean the surface of dryer rolls in order to prevent the buildup of fibers and other debris on the surface of the cylindrical dryer roll. U.S. Pat. No. 3,003,176, 1961, Goyette, and U.S. Pat. No. 3,292,201, 1966, Bedard, each describe the use of a hood extending along the edge of the doctor blade combined with air blowers which direct an airstream longitudinally of the hood to move the debris collected by the doctor blade. A suction device may be provided at one end of the hood in order to provide an exhaust for the hood to remove the contaminants from the airstream.
The hoods and blower mechanisms of the above prior art are mounted on the support for the doctor blade and can be pivoted and adjusted relative to the doctor blade edge. These supports are generally rigid, and the mounting of the contaminant removal mechanism does not pose too much of a problem although the doctor support mechanism is often masked by this additional structure and adjustment of the doctor blade may become difficult. Since the hoods are generally mounted on the doctor blade support, they must extend forward of the blade edge upstream of the direction of rotation of the roll, and over the surface of the roll. Thus, a flexible skirt must be provided which will be in contact or at least closely associated with the moving surface of the roll upstream of the blade edge. Thus, the hood will be subject to wear because of friction and may also accumulate debris on the outside surface of the hood, requiring further cleaning.
Due to the high speed of the rolls, a boundary layer is formed which moves in the same direction as the roll, thus against the leading edge of the hood or the skirt on the hood. This boundary layer may be at least 0.5 inch thick, thereby reducing the energy efficiency of the prior art devices since enhanced suction devices are required.
Since the known contaminant removal systems extend upstream in a cantilever manner, they can only deflect forwardly and away from the surface of the roll, which might be damaged in the event of a paper break.
Modern doctor blades are often mounted on pneumatic doctor blade support mechanisms which are flexible in nature and cannot support a contaminant removal system of the type described in the prior art.